1. Field of the Invention
The present invention relates particularly to a connected structure of a receptacle terminal with a pin terminal consisting of a tab, a round pin, a square-section pin or another type pin. The receptacle terminal has a contact therein for catching the pin terminal. The present invention also relates to a receptacle terminal itself receiving a pin terminal for electrical connection thereof and having a structure for reliable connection of the receptacle terminal with the pin terminal.
2. Related Art
Terminals are generally used for electrical connection of various types of electric appliances and switches. There are provided receptacle terminals and pin terminals for detachably connecting electrical cables to the appliances and switches. The receptacle terminal generally has a resilient tongue piece urged against the pin terminal inserted into the receptacle terminal for electrical connection thereof.
The pin terminal generally consist of a tab, a round pin, a square-section pin, or another type pin. The square-section pin type terminals are generally used for a print circuit board. Furthermore, pin type terminals are also used in a connector, and the terminals are joined to conductors disposed on the print circuit board.
A conventional technical art related to the terminals is disclosed in Japanese Utility Model Application Laid-open No. 61-87475, Japanese Utility Model Laid-open No. H. 4-61775, or Japanese Patent Application Laid-open No. H. 11-233181. Japanese Utility Model Application Laid-open No. 61-87475 describes a terminal decreased in material to achieve a reduced cost. Japanese Utility Model Application Laid-open No. H. 4-61775 describes a socket type contact for preventing a damage of a spring of the terminal. Japanese Patent Application Laid-open No. H. 11-233181 describes a terminal fitting for providing an adequate contact pressure between male and female terminal pieces and for allowing a smooth engagement of the terminal pieces.
Referring to FIGS. 9 to 11, a conventional terminal will be discussed hereinafter. FIG. 9 is an illustration for showing a contact state of a receptacle terminal and a pin terminal. FIG. 10 is a general longitudinal sectional view showing a connection structure of a receptacle terminal 1xe2x80x2 and a pin terminal 2xe2x80x2.
The receptacle terminal 1xe2x80x2 is made of a metal material and has a contact Axe2x80x2 providing a contact line, a contact Bxe2x80x2 providing a contact area, a resilient tongue piece 3xe2x80x2, an accommodation chamber Rxe2x80x2, a receptacle terminal securing member 4xe2x80x2, a conductor connection member (not shown) for crimping an electrical cable, and an insulator crimping piece (not shown) for securing an isolator of an electrical cable. The accommodation chamber Rxe2x80x2 has a rectangular shape constituted by a top plate 7xe2x80x2, a bottom plate 8xe2x80x2, and a pair of side walls SWxe2x80x2. The resilient tongue piece 3xe2x80x2 has a fold 11xe2x80x2 and a free end 12xe2x80x2. Under the resilient tongue piece 3xe2x80x2, there is provided a deflection restricting member 14xe2x80x2 for the resilient tongue piece.
The fold 11xe2x80x2 of the resilient tongue piece 3xe2x80x2 provides a reaction force against a compressive deformation thereof. Furthermore, the free end 12xe2x80x2 of the resilient tongue piece 3xe2x80x2 contacts the bottom plate 8xe2x80x2 of the receptacle terminal, while each of them keeps a resilient force, increasing the reaction force of the resilient tongue piece 3xe2x80x2. The reaction force allows the pin terminal 2xe2x80x2 to get caught between the resilient tongue piece 3xe2x80x2 and the top plate 7xe2x80x2 of the receptacle terminal. For any easy insertion of the pin terminal 2xe2x80x2 into the receptacle terminal 1xe2x80x2, the pin terminal 2xe2x80x2 has a tapered tip 13xe2x80x2.
FIG. 11 is a sectional view taken along line Y2xe2x80x2xe2x80x94Y2xe2x80x2 of FIG. 10. The receptacle terminal 1xe2x80x2 has a box-shaped section for receiving the pin terminal 2xe2x80x2 to allow electrical connection thereof. The contact A of the resilient tongue piece 3xe2x80x2 contacts the pin terminal 2xe2x80x2 to define a contact line.
Meanwhile, the contact Bxe2x80x2 provided in the top plate 7xe2x80x2 contacts the pin terminal 2xe2x80x2 to define a contact area. The pin terminal 2xe2x80x2 has a generally square section having four round corners 9xe2x80x2 and four straight lines 10xe2x80x2 connecting the corners.
The receptacle terminal 1xe2x80x2 has a first contact Axe2x80x2 which is a peak of the resilient tongue piece 3xe2x80x2 and a second contact Bxe2x80x2 of a flat surface, which holds a tab of the pin terminal 2xe2x80x2 and makes the receptacle terminal 1xe2x80x2 contact with the pin terminal 2xe2x80x2. The contact state is a combination of a point contact and a flat surface contact (see FIG. 9).
FIG. 12 is a partial enlarged sectional view showing a contact portion of the receptacle terminal 1xe2x80x2 and the pin terminal 2xe2x80x2, which is surrounded by an ellipse C of FIG. 10. The view illustrates a detailed contact state in which the terminal top plate 7xe2x80x2 of the receptacle terminal 1xe2x80x2 has been contacting the pin terminal 2xe2x80x2.
Next, a frictional resistance produced by the contact area when the pin terminal slides will be discussed. The receptacle terminal 1xe2x80x2 has a number of minute pits and projections (roughness) as well as the pin terminal 2xe2x80x2 as illustrated in the enlarged view of FIG. 12. The resilient tongue piece 3xe2x80x2 exerts an urging force Faxe2x80x2 on the pin terminal 2xe2x80x2, while the pin terminal 2xe2x80x2 also receives a reaction force Fbxe2x80x2 form the receptacle terminal 1xe2x80x2. With the urging forces, the pin terminal 2xe2x80x2 slides in the receptacle terminal 1xe2x80x2, so that a frictional force Fxe2x80x2 is produced between the receptacle terminal 1xe2x80x2 and the pin terminal 2xe2x80x2. That is, the pin terminal 2xe2x80x2 overcomes the frictional force Fxe2x80x2 to move in the receptacle terminal 1xe2x80x2.
When the force Faxe2x80x2 urges the pin terminal 2xe2x80x2 against the receptacle terminal 1xe2x80x2, highest peaks of projections of the contact surfaces may engage with associated opposed portions of the contact surfaces. This engagement of the peaks is called as an actual contact hereinafter.
In FIG. 12, an actual contact occurs at contact portions T1 and T2. Meanwhile, an apparent engagement of the contact surfaces appears over a range Tx.
At the actual contact portions T1, T2, the receptacle terminal 1xe2x80x2 and the pin terminal 2xe2x80x2 are engaged with each other by adhesion forces of the contacting bodies. This adhesion force engagement produces a friction force Fxe2x80x2 at a shear movement of the contacting bodies.
As far as the adhesion force engagement is maintained, a reliable electrical connection is accomplished between the contact surfaces. However, minute sliding movements of the contacting bodies due to an external vibration force or the like wear away the projections of the contact surfaces. Thereby, the contact surfaces are brought to another contact state, causing an unstable electrical connection thereof.
Next, referring to FIG. 13, another conventional terminal 1xe2x80x3 will be discussed. The receptacle terminal 1xe2x80x3 is made of a metal material and has two opposed contacts Axe2x80x3, Bxe2x80x3 each providing a contact line, a resilient tongue piece 3xe2x80x3, an accommodation chamber Rxe2x80x3, a pin terminal entrance INxe2x80x3, a conductor connection member (not shown) for crimping an electrical cable, and an insulator crimping piece (not shown) for securing an isolator of an electrical cable. The accommodation chamber Rxe2x80x3 has a rectangular shape constituted by a top plate 7xe2x80x3, a bottom plate 8xe2x80x3, and a pair of side walls SWxe2x80x3.
The resilient tongue piece 3xe2x80x3 has a base 11xe2x80x3 and a free end 12xe2x80x3. Under the resilient tongue piece 3xe2x80x3, there is provided a deflection restricting member 14xe2x80x3 for the resilient tongue piece. The deflection restricting member 14xe2x80x3 has a resiliency for resiliently supporting the resilient tongue piece.
The receptacle terminal 1xe2x80x3 illustrated in FIG. 13 has a first contact Axe2x80x3 which is a peak of the resilient tongue piece 3xe2x80x3 and a second contact Bxe2x80x3 positioned near the base thereof. The two contacts hold a pin terminal (not shown) and makes the receptacle terminal 1xe2x80x3 contact with the pin terminal.
As illustrated in FIGS. 10 and 11, the receptacle terminal 1xe2x80x2 has the upper contact Bxe2x80x2 which is a flat inner surface of the top plate 7xe2x80x2. Furthermore, the pin terminal 2xe2x80x2 also has a flat surface for contacting the upper contact Bxe2x80x2. That is, the contact Bxe2x80x2 provides a contact area for the pin terminal 2xe2x80x2.
However, the area contact of FIG. 10 provides a pressure "sgr"bxe2x80x2 at the contact Bxe2x80x2, which is smaller than another pressure "sgr"axe2x80x2 that is produced by a point contact or a line contact at the contact Axe2x80x2. In FIG. 10, the pressure "sgr"bxe2x80x2 is illustrated by a plurality of short arrows distributed in a comparatively wide area of the contact Bxe2x80x2.
During an engagement state of the receptacle terminal 1xe2x80x2 with the pin terminal 2xe2x80x2 of FIG. 10, minute movements of the pin terminal 2xe2x80x2 relative to the receptacle terminal 1 may occur, since the contact Bxe2x80x2 is provided with a comparatively low pressure "sgr"bxe2x80x2. The minute movement produces a friction at the contact Bxe2x80x2. Since the minute movement is repeated, an electrical connection of the contact Bxe2x80x2 becomes unstable.
Furthermore, in the connection structure of FIG. 10, the contact Bxe2x80x2 provides an area for electrical connection while the contact Axe2x80x2 provides a line for electrical connection with the pin terminal 2xe2x80x2. Thus, the contact Axe2x80x2 receives the contact pressure "sgr"axe2x80x2 larger than the contact pressure "sgr"bxe2x80x2 of the contact Bxe2x80x2. Accordingly, the contact Axe2x80x2 may minutely move, causing a frictional wear of the contact Axe2x80x2.
If the contact tab of the pin terminal has a longitudinal deflection as illustrated in a second variation of FIG. 9, the receptacle terminal contacts the pin terminal so as to have two contact points. In that sate, a deviation of the two contact points provides a bending force to the pin terminal, causing an unstable electrical connection of the receptacle terminal 1xe2x80x3 and the pin terminal 2xe2x80x2.
In view of the above-mentioned disadvantage, an object of the present invention is to provide a receptacle terminal and a connection structure of the receptacle terminal with a pin terminal, which eliminate an unreliable electrical connection to guarantee a sure, stable electrical connection of the receptacle terminal and the pin terminal for a long service time.
For achieving the object, a receptacle terminal of a first aspect of the invention includes:
a plurality of first contacts disposed in parallel with each other on an inner surface of a first plate of the receptacle terminal and arranged in an insertion direction of an associated pin terminal and
a resilient tongue piece opposed to the first plate and having at least one second contact. The second contact of the resilient tongue piece is positioned between the first contacts.
In the constitution of the receptacle terminal, the contact of the resilient tongue piece is configured substantially in the same way as the prior-art receptacle terminal. However, the contact of the first plate of the receptacle terminal according to the present invention allows a stable electrical connection. Accordingly, the receptacle terminal eliminates the disadvantage of an unstable electrical connection of the prior-art contact.
Furthermore, the contact of the receptacle terminal first plate receives an appropriate contact pressure, allowing an adequate friction for the pin terminal to slide thereon. Accordingly, the contact of the receptacle terminal first plate maintains its performance for a longer time.
Preferably, the second contact of the resilient tongue piece is positioned between the first contacts in a longitudinal direction of the receptacle terminal.
Such arranged contacts of the receptacle terminal first plate allow the pin terminal to be appropriately inserted into the receptacle terminal. Thus, the receptacle terminal can reliably electrically connect to the pin terminal.
Preferably, the first contacts of the receptacle terminal each are located substantially at the middle of the first plate of the receptacle terminal in a lateral direction of the receptacle terminal.
Such arranged contacts of the receptacle terminal first plate prevent a lateral inclination of the pin terminal which has ben received in the receptacle terminal. Thus, the pin terminal can reliably electrically connect to the receptacle terminal.
Preferably, the first plate of the receptacle terminal has a gentle curvature portion connecting the first contacts in a longitudinal direction of the receptacle terminal, and the gentle curvature portion is located inside from a general surface of the first plate.
The gentle curvature allows an easy bending process of the first plate made of a metal material. Furthermore, the gentle curvature causes neither cracks nor residual stresses in the metal plate. In addition, the receptacle terminal first plate can be easily formed with the plural contacts for a stable electrical connection thereof.
A receptacle terminal of a second aspect of the invention includes a plurality of first contacts electrically connected to a pin terminal. The receptacle terminal can catch the associated pin terminal with all the contacts being electrically connected to the pin terminal.
Such arranged contacts receive contact forces distributed for them, so that a frictional wear of each contact will develop substantially in the same way as each other.
Thus, only one of the contacts does not experience such a considerable frictional wear as appears in the prior art having a contact arrangement that causes an extremely uneven distribution of the contact forces. Moreover, the pin terminal surely gets caught between the contacts of the receptacle terminal, allowing a stable, sure electrical connection thereof.
A connection structure of a receptacle terminal with a pin terminal according to a third aspect of the invention includes a plurality of first contacts formed on the receptacle terminal for electrical connection with the pin terminal. At least one of the contacts can electrically connect to the pin terminal when the pin terminal has been inserted in the receptacle terminal, and the pin terminal is rectangular in its lateral section. The pin terminal has at least one outer curved surface gently outwardly swelled for connection to the pin terminal.
The such configured receptacle terminal has a smaller total contact area, so that the pin terminal is surely caught by the receptacle terminal. Thereby, a stable, reliable electrical connection thereof can be achieved.
The connection structure of the receptacle terminal and the pin terminal may provide a line contact state.
Alternatively, all the contact surfaces of the pin terminal may be curved. The engagement of the receptacle terminal with the pin terminal allows a point contact state thereof. The receptacle terminal can surely catch the pin terminal with the reaction force of the resilient tongue piece of the receptacle terminal, allowing a stable, reliable electrical connection of the terminals.
Preferably, the connection structure of the receptacle terminal and the pin terminal may have the receptacle terminal described in the first aspect of the present invention. Thereby, the receptacle terminal can surely catch the pin terminal, allowing a stable, reliable electrical connection of the terminals.